Well I wouldn't send my melee fighter into battle without either hiding him around a corner so he isn't shot or giving him a personal shield, so why would I use animals who can't do either of those things and who can't be given artificial enhancements should they lose a limb? At this point animals are just crappy melee fighters.
That said, a pack of huskies make for great post-battle clean-up.
That said, a pack of huskies make for great post-battle clean-up.